Paint Driers

Paint driers (dryers) accelerate the chemical reaction that occurs as an oil paint cures. Artists, house painters and sign painters have used driers, such as Japan Drier, for years to accelerate drying. These driers can be useful when you need to paint two coats in one day.

“Driers are also useful if you are in a hurry lettering a sign or a truck,” says veteran sign painter, Joe Balabuszko. “Driers save time if you want to outline the copy the same day you paint the letters. They also same time if you are repainting an existing sign.”

Joe explains that after tracing the outline of the lettering with an indelible pencil, you can paint the background color with a little drier in it. The indelible pencil shows thru the background color. “The drier allows you to paint the lettering the same day,” Balabuszko says. “The time you save is money in your pocket.”

Here’s how paint driers work. Oil paint consists of drying oil and pigment. The paint cures as the resin or binder, such as linseed oil, polymerizes and then cross-links. Driers work as catalysts to promote the oxidation of the oil and to accelerate the cross-linking process, in which oil molecules join together.

Many years ago, driers were lead based. Lead driers were popular for several reasons. Their use toughened the paint film, making it more flexible and more durable.  Because of the toxicity of lead, other elements have replaced it.  These materials include iron, zinc and zirconium. Some, but not all, of the driers are colorless. Cobalt driers are bluish. Iron driers have a reddish hue.

Modern paint driers are generally manufactured by dissolving a metallic salt in a hydrocarbon solvent, such as mineral spirits, to form a metal soap. The metallic salt results from a chemical reaction between a metal and an organic acid, such as hydrochloric acid or sulfuric acid. In this reaction the metal replaces hydrogen (H₂) in the acid. In other words, the result of the reaction is a metallic salt and hydrogen gas..

While the drier helps the paint to harden, misuse of the product has some potential disadvantages. These disadvantages include embrittlement of the paint film leading to cracking; darkening of the paint; and skinning over of the paint resulting in wrinkling.

When using a paint drier, here are some general rules that you should follow:

  • Read the manufacturer’s instructions and safety precautions before use. Do not exceed the recommended amount. Typically, you should not add more than 5% of drier to your paint.
  • Some paints dry well on their own. Only use a drier unless absolutely needed.
  • Do not mix in the drier until you are ready to use the paint.
  • Do not add more than one type of drier to